Adequate sensory function in the oral cavity is important to the overall appreciation of foods and to maintenance of good nutritional status. Increasingly, chemosensory scientists have attended to the contribution of sensations besides the four classical taste qualities in oral chemical perception. The broad goals of this work are to describe and quantify human reactions to one important class of trigeminally-mediated oral sensations, namely those of astringent materials. Astringent sensations produced by single compounds have received little attention from the chemosensory community in spite of their importance in foods. This work is designed to remedy that deficiency by controlled psychophysical evaluations of simple aqueous solutions of single compounds and two-component mixtures. Particular attention will be paid to the time-course and different qualities of sensations evoked by astringent stimuli. Three experiments are planned: 1) quantitative and qualitative assessments of perceived astringency from different chemical stimuli over time, 2) structure- activity studies of selected series of tannin compounds previously shown in vitro to vary in phenol-protein binding and are thus predicted to vary in perceptual astringency in vivo, and 3) a study of mixtures of astringent materials, to bridge the gap between single-compound studies and more complex food systems as well as provide information on interactions (synergy, masking) that have implications for the number of underlying mechanisms. Finally, since salivary flow rate is highly variable among individuals, and since salivary flow could affect astringent sensations by a number of mechanisms, flow rate will be assessed as a potentially important covariate of perceptual reactions to astringent materials in the first and second experiments in this plan. While the primary focus of this work is to provide a rich source of descriptive and hypothesis-generating information on a poorly understood class of oral chemical stimuli, the proposed research will have also have implications for understanding the mechanisms underlying astringency and individual differences in reactions to astringent compounds.